Disease poses grave threat to forests

Plant scientists have warned that commercial forestry plantations and world heritage rainforests could be at risk after state and federal governments decided not to eradicate an outbreak of a tree disease when it was detected in April.

The federal Department of Agriculture, Fisheries and Forestry maintains that the disease, which was first detected at a cut-flower nursery on NSW’s Central Coast, is myrtle rust and not guava rust, which attacks eucalypts.

But the president of the Australasian Plant Pathology Society, Caroline Mohammed, said analysis of DNA samples of contaminated plants showed a 99 per cent similarity to guava rust, one of the gravest threats to Australia’s native flora.

The department’s advice says that guava rust, which comes from South America, causes serious damage in eucalypt plantations and can deform or even kill trees, diminishing growth rates and plantation productivity.

Dr Mohammed said it was of concern that state and federal authorities had decided in April that they would not attempt to eradicate the disease and that infected plants were being sprayed with fungicide, rather than being destroyed.

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“Given the potential risks of this incursion, there should have been ­immediate eradication measures, which include plant destruction and compensation for the property owner," she said.

“The response from Australian ­authorities has been very slow. There was a premature decision to come out of the emergency phase, under which you eradicate."

Dr Mohammed said it was difficult to know how the rust would ­behave in Australia, but it could ­become established in forest hardwoods, garden plants and cut flowers and potentially take out certain species from heritage-listed rainforests.

A May 4 statement from DAFF said a decision had been taken on April 30 that eradication was not feasible. It said the rust had been ­detected in willow myrtle, turpentine and bottlebrush species but had not been confirmed in Australian eucalypts.

Elders Forestry spokesman Adam Redman said the company was closely monitoring developments. “Guava rust is a serious disease," he said.

Coalition agriculture spokesman
John Cobb
said the government had added to confusion by refusing to take the threat seriously.

He said the rust could also jeopardise massive amounts of carbon stored in forests.

A DAFF spokeswoman said yesterday that the disease had been confirmed as myrtle rust, based on the spore structure and host range, but infection levels were low and fungicides were proving effective.

“It is likely that the disease has been present for long enough to have spread over a wide distance. This, ­together with the location of the infected properties near large tracts of native bush and the rust’s wide host range, makes the detection and ­destruction of the disease impossible," she said.